WASHINGTON — The Environmental Protection Agency took a historic step on Tuesday in the fight against climate change, proposing the first limits of greenhouse gas emissions from new power plants.

The new rule likely would make new coal-fired power plants too expensive after this year. It wouldn't apply to some 15 power plants that are expected to break ground in the next 12 months. After that, however, coal-fired plants would have to capture and store some of their carbon dioxide emissions, a practice that's currently so costly that it isn't in commercial use anywhere.

Natural gas plants belch only about half the emissions of coal plants and would not need any additional equipment to meet the new standard. The nation's utilities have been moving toward natural gas to fuel new plants anyway, since the use of hydraulic fracturing has greatly expanded the nation's gas supply and prices are down.

This is the first time that the United States has ever proposed any limits on greenhouse gases from industrial sources. Republicans in Congress and their business allies vowed to fight the EPA rule as hostile to abundant coal and too costly. Environmentalists and health groups cheered it.

Scientists have amassed a huge body of evidence and documented research showing that these gases in the atmosphere, mostly from burning fossil fuels, are driving ocean acidification and global warming.

"We know the potential impacts of climate change touch everything from tourism to agriculture and will have an extraordinary environmental and economic footprint if allowed to proceed unchecked," said EPA Administrator Lisa Jackson. "And when we see the extraordinary potential for cleaner, cheaper energy for the American people and the chance to lead a global marketplace for clean-energy technology, it is clear that we must take action."

The standard will have limited impact, however, because it won't apply to existing power plants, the biggest industrial source of greenhouse gases. Also exempt are new plants that already have permits and will break ground in the next 12 months.

Jackson said the EPA has no plans to address emissions from existing plants. U.S. power plants produced 2.3 billion metric tons of carbon dioxide in 2010, about one-third of the nation's total emissions.

She addressed economic criticism by saying that the new standard takes advantage of abundant natural gas and imposes no costs on current plants. She also said that coal would remain a major part of the U.S. energy mix, citing Energy Department forecasts.

Coal now generates 45 percent of electricity. The department expects it will still provide 29 percent in 2035.

Republicans brushed away Jackson's assurances.

"With gas prices already soaring, American families and small businesses now stand to face higher electricity bills, and they have this administration's policies to thank," House Speaker John Boehner, R-Ohio, said in a statement.

"President Obama and EPA Administrator Lisa Jackson are circumventing the will of Congress and the American people by moving forward with a regulation that threatens our most abundant, reliable and affordable domestic electricity source — coal," said Rep. Ed Whitfield, R-Ky., chairman of the House subcommittee on energy and power.

Republicans have made what they call the Obama administration's "war on coal" an election-year issue. They oppose any limits on greenhouse gases and the administration's other pollution-control efforts. They also argue that the shift from coal to natural gas will cost jobs and raise electricity costs.

Whitfield sent a letter to the White House Office of Management and Budget in February signed by 205 House Republicans and 14 Democrats objecting to the standard for new power plants.

The U.S. Chamber of Commerce also opposed the rule, claiming it would lead to higher costs. "The chamber will be evaluating all of its options to overturn this rule if it is ultimately issued," said Bruce Josten, its vice president for government affairs.

The EPA next will take comments and hold hearings on the proposed rule; it could change the rule before it becomes final. No date is set for when it becomes final.

Meanwhile, industry groups have challenged the EPA on greenhouse-gas regulation in court. The U.S. Court of Appeals for the District of Columbia heard arguments in February. The court's eventual ruling could block the EPA from moving ahead with greenhouse gas regulations.

The new proposal would require new fossil fuel plants to emit no more than 1,000 pounds of carbon dioxide per megawatt-hour of electricity produced. The EPA said that 95 percent of all new natural gas combined-cycle power plants should be able to meet the standard without extra pollution controls.

The proposal would allow new coal plants to average their emissions over 30 years. They could start with higher emissions but would have to cut them sharply to meet the standard over that period, Jackson said. She said 50 percent of emissions would have to be captured at coal plants and kept out of the atmosphere.

Some states, including Illinois and Montana, already require carbon capture and storage technology for new coal plants.

Environmental and health groups cheered the EPA's proposal.

"Power plants should not be allowed to emit unlimited amounts of carbon pollution into the air," Albert A. Rizzo, a physician and chair of the American Lung Association's board of directors, said in a statement.

Warming from a buildup of greenhouse gases in the atmosphere also will increase smog levels, and "more smog means more childhood asthma attacks and complications for those with lung disease," Rizzo said.

"These first-ever carbon pollution standards for new power plants mean that business as usual for the nation's biggest sources of carbon pollution, dirty coal-burning utilities, is over," Sierra Club executive director Michael Brune said in a statement.